MHD Air Breathing Propulsion and Power for Aerospace Applications

This Defense Intelligence Reference Document, dated 21 November 2010, provides a technical overview of magnetohydrodynamic (MHD) and plasma-based propulsion concepts for aerospace applications. Prepared under the Advanced Aerospace Weapons System Applications (AAWSA) Program, the report evaluates the feasibility of using ionized gases to enhance propulsion and aerodynamic performance. The document is divided into chapters covering concept overviews, aeronautical applications, space applications, and a summary of predictions. The author examines the physics of weakly ionized plasmas, noting that while they offer potential for drag reduction, flow control, and propulsion enhancement, they face significant hurdles. These include the high energy cost of ionization, the need for strong magnetic fields, and the weight and complexity of the required hardware. The report specifically critiques the 'Ajax' concept, a Russian-originated propulsion idea, concluding that it is largely ineffective at speeds below Mach 12. Conversely, the document highlights the 'reverse energy bypass' and 'virtual cowl' as more practical approaches for hypersonic vehicles, particularly when integrated with high-power onboard energy sources like nuclear reactors. Regarding space applications, the document notes that electric propulsion is already established for satellite station-keeping and positioning. It predicts a continued shift toward electric systems for spacecraft, driven by the need for greater maneuverability and longer mission durations. The report concludes that while MHD propulsion for hypersonic flight remains a challenging technological goal, it is a field of interest for nations including Russia, China, and Japan, and could become viable within a decade if advancements in lightweight magnets and power sources are achieved.